Solution-processed transparent blue organic light-emitting diodes with graphene as the top cathode

Abstract

Graphene thin films have great potential to function as transparent electrodes in organic electronic devices, due to their excellent conductivity and high transparency. Recently, organic light-emitting diodes (OLEDs)have been successfully demonstrated to possess high luminous efficiencies with p-doped graphene anodes. However, reliable methods to fabricate n-doped graphene cathodes have been lacking, which would limit the application of graphene in flexible electronics. In this paper, we demonstrate fully solution-processed OLEDs with n-type doped multilayer graphene as the top electrode. The work function and sheet resistance of graphene are modified by an aqueous process which can also transfer graphene on organic devices as the top electrodes. With n-doped graphene layers used as the top cathode, all-solution processed transparent OLEDs can be fabricated without any vacuum process.

Flexion bonding transfer of multilayered graphene as a top electrode in transparent organic light-emitting diodes

“…The total luminance of the G-TOLED is comparable to that of the Ag-TOLED. In addition, total maximum luminance of G-TOLED is 44,293 cd m −2 (23,428 cd m −2 for bottom and 20,865 cd m −2 for top) at 13 V which is about 43 times higher compared to previously reported value 8 . These results suggest a successful lamination and subsequent uniform hole injection of the MLG top electrode.…”

“…Therefore, efficient TCTEs in OLEDs should have high optical transmittance and electrical conductivity, and they should not damage the organic layers during the deposition process. Moreover, it is necessary to obtain the appropriate energy level alignment between the organic layer and TCTE in order to facilitate efficient charge injection 8 .…”

“…TCTEs composed of a wide variety of materials have been developed, including semi-transparent metals (STMs) 5 9 10 11 , transparent conducting oxides (TCOs) 12 13 , conducting polymers 14 15 , carbon nanotubes (CNTs) 16 17 18 , silver nanowires (AgNWs) 19 , and graphene 8 20 21 . In conventional TOLEDs, TCOs and STMs are the materials of choice for commercial use, as the bottom and top electrodes, respectively.…”

“…However, it is difficult to deposit graphene onto organic layers directly, because of the high required synthesis temperature 25 . Previously reported graphene top electrodes in light-emitting devices have been prepared using wet transfer method or high-temperature thermal treatment 8 20 . These graphene transfer processes limit the materials and structures of these devices, leading to poor device performance.…”

The effect of transmittance and luminous efficiency with the application of cathode mesh mask in transparent organic light‐emitting devices

“…For this purpose, many researchers began to try a variety of alloy cathodes and laminated composite cathodes preparation, and dielectric/metal/dielectric composite structure as a TOLED cathode. In addition, in order to enhance light outcoupling, some researchers have also made efforts, such as the use of some new materials, graphene, PEDOT:PSS, quantum dots materials, and nanomaterials. There has been so many application of nanomaterials, such as using Ag nanoparticles modified ITO, silver nanowire (Ag NW) with organic polymer materials, nanocomposite film, and so on.…”